If you want to be happy, living near a park could be a good idea. More and more research shows a relationship between green space and higher levels of mental health.

The latest comes from the University of Wisconsin-Madison. Researchers looked at 2009 survey data that asked 2,500 residents about depression, anxiety, and stress. They next analyzed 229 neighborhoods for vegetation cover. Those places with more trees tended to be happier, and the association was “significant and sizable,” according to a paper discussing the results.

Those places with more trees tended to be happier, and the association was “significant and sizable.”

In fact, the relationship of happiness to trees was similar to well-known correlations, like unemployment. “The most interesting thing is that decreased symptoms attributed to green space were similar to decreases observed for other important determinants of mental health, including insurance status and income,” wrote Kirsten Beyer, an assistant professor at the Medical College of Wisconsin, in an email.

The paper shows the difference in well-being levels between areas with zero tree canopy cover and 100% canopy cover was greater than the well-being difference between someone having and not having health insurance.

The research, which is published in the International Journal of Environmental Research and Public Health, could provide further reasons to invest in green space, the authors write. “Our work indicates that ‘greening’ could be considered a potentially low-cost, high-return investment among urban and regional planners to positively influence population mental health,” they say.

In other words, don’t just invest in parks because they look nice and offer exercise for joggers. Do it to make people feel better, too.